1. Field of the Invention
High-temperature fuel cells are utilized for the conversion of chemical energy into electric energy. Devices for electrochemical energy conversion gain importance thanks to their simple handling and their high efficiency.
The present invention relates to the further development of the electrochemical high-temperature cells with the use of ceramic solid electrolytes as ion conductors, and the device is to be largely independent of the fuel used.
The invention further relates to a device for the conversion of chemical energy into electric energy by an electrochemical high-temperature process by use of flat, plane ceramic fuel cells, arranged like a stack, on the basis of zirconium oxide as solid electrolyte, and each fuel cell is acted on, on the one side, by the gaseous oxygen carrier and, on the other side, by gaseous fuel.
2. Description of the Related Art
Electrochemical units for the conversion of the chemical energy, contained in a gaseous fuel, into electric energy are known. The fuel cells made so far work mainly with hydrogen or carbon monoxide, optionally with a mixture of these two fuels. If hydrocarbons such as, for example, methane (main component of natural gas) are available, they are generally first converted by a conversion process into a mixture of hydrogen and carbon monoxide. Since these processes proceed endothermally, they are connected with a considerable outside heat consumption. For this purpose, separate conversion units are generally operated and the heat requirement is covered by combustion of a part of the gaseous fuel. For this purpose, additional preparation units for steam or carbon dioxide are necessary.
In the related art, the following publications are named:
O. Antonsen, W. Baukal and W. Fischer, "High-temperature Fuel Battery with ceramic electrolytes," Brown Boveri Mitteilungen [information] January/February 1966, pp. 21-30,
U.S. Pat. No. 4,692,274
U.S. Pat. No. 4,395,468
W. J. Dollard and W. G. Parker, "An Overview of the Westinghouse Electric Corporation solid oxide fuel cell program," Extended Abstracts, Fuel Cell Technology and Applications, International Seminar, The Hague, the Netherlands, Oct. 26-29, 1987,
F. J. Rohr, High-Temperature Fuel Cells, Solid Electrolytes, 1978 by Academic Press, Inc., p. 431 ff.
D. C. Fee et al., Monolithic Fuel Cell Development, Argonne National Laboratory, Paper presented at the 1986 Fuel Cell Seminar, Oct. 26-29, 1986, Tucson, Ariz., U.S. Department of Energy, the University of Chicago.
The known devices necessary for conversion of primary fuels, especially of hydrocarbons, into more suitable gaseous fuels (H2 and CO) are expensive and require additional delivery means and control elements (pumps, valves, etc.). Also such an operation requires an additional fuel consumption, by which the efficiency is reduced.
The designs known so far of ceramic fuel cells and cell batteries leave much to be desired in regard to unit volume, power and efficiency as well as guiding the current of gaseous media. Therefore, there is a great demand to improve fuel cells and their arrangement in design and operational respect.